Sound isolating (SI) earphones and headsets are becoming increasingly popular for music listening and voice communication. SI earphones enable the user to hear an incoming audio content signal (whether speech or music audio) clearly in loud ambient noise environments, by attenuating the level of ambient sound in the user ear-canal.
To maximize situation awareness and enable an SI earphone user to hear their local ambient environment, SI earphones often incorporate ambient sound microphones to pass through local ambient sound to the loudspeaker in the SI earphone. Sound isolating earphones can also incorporate an ear canal microphone for detecting the earphone user voice with an improved signal to noise ratio over using an external ambient sound microphone to detect the voice. The ear canal microphone signal can be further processed with noise reduction algorithms and directed to a mobile device for voice communication purposes, e.g. for voice activated machine control or in a telephone call with a remote individual.
Recording and processing of the ambient sound microphone signals and ear canal microphone signals can provide benefits for the user: for archival of ambient sound recordings (e.g. binaural recordings) or for further processing e.g. for noise reduction. However, the analog audio input to most mobile phones and other mobile computing devices often only allow for a single, “mono” audio channel to be received. A need therefore exists to enable the mobile computing device to receive more than one audio input channel from an earphone or pair of earphones that contain multiple microphone signals.